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We use storage array features to clone LUNs and then map these "new" LUNs out again to the same or different hosts. A typical case is when we refresh between environments, so imagine cloning a LUN holding a bunch of VMs from source host TEST1 to destination host TEST2. Sometimes the destination host will assign the drive automatically, and sometimes it won't. The storage array changes the cloned LUN's serial number (but we could modify it back) but for the rest the cloned LUN contents are identical to the source. In the case of a refresh (so in this example remove the old LUN from TEST2 and then map the cloned LUN in it's place) the LUN ID also stays the same. The LUNs are accessed over a Fibre Channel SAN and are thus not seen as removable devices. Needless to say, in the situation here we are not cloning the boot LUN itself either.

I found Microsoft KB234048 describing the behavour with Windows 2000 but I suspect a lot has changed in the last 10 years.

If anyone has details, including special cases like if they are MSCS shared disks, or multiple disks with matching signatures (i.e.cloned disk is maped to same server), please share!

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up vote 1 down vote accepted

Well, actually not much has changed - the associations are still stored in the registry within the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices key. Some insight about what to put in there / how to interpret the data comes from this 3rd party docs.

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I didn't see mount points in the MountedDevices registry key. How are these associations known? Also, many MountedDevices entries are more than 12 bytes, how do I interpret these? – Chris Madden May 18 '11 at 14:49
The mount points are filesystem references to volume objects - they are saved as JUNCTION objects in NTFS which you can see when using "dir" for example: 18.05.2011 22:36 <JUNCTION> MountTest [\??\Volume{<VolumeGUID>}\]. The reference is taken to the value within the MountedDevices key. Values in MountedDevices which are longer than 12 bytes are typically removable storage devices referenced by their device string and a volume GUID in Unicode. – the-wabbit May 18 '11 at 20:45

For cluster storage, Windows looks at the MBR Signature or GPT Guid (depending on disk format) to identify the disk so that it can be used on other nodes in the cluster. If two disks show up with duplicate signatures/guids I believe the first one is used and the others are left offline. If you want a cloned disk to show up as a new disk, you'll need to change the signature/guid.

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